Petra finds a discolored stain on the carpet at a suspected crime scene. What two presumptive tests might she use to determine if the stain is blood? First, Petra sprays the discolored area with , which returns a glowing blue color. However, she knows that this chemical might also turn blue with other substances that contain iron. Subsequently, she uses , which turns pink, indicating the presence of hemoglobin.

First, Petra sprays the discolored area with  

Fluorescein

, which returns a glowing blue color. However, she knows that this chemical might also turn blue with other substances that contain iron. Subsequently, she uses  

Phenolphthalein

, which turns pink, indicating the presence of hemoglobin.

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation:

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